Deaf persons communicate effectively with each other by means of manual signs. What is the place of signs in the internal cognitive operations of the deaf? The general approach taken to this question is to compare the functions of signs for the deaf with those of speech for the hearing. Two methods of investigation are proposed to tackle this question. One is designed to test to what extent deaf subjects represent information in memory through the medium of signs. The second method involves testing whether the signs of the deaf are processed more effectively in the left cerebral hemisphere, which is dominant for speech and language, than in the right hemisphere. This will be tested by means of brief tachistoscopic exposure to the right and left visual fields, which are connected respectively to the left and and right cerebral hemispheres.